The ability to reduce the surface tension of water is of great importance in waterborne coatings, inks, adhesives, and agricultural formulations because decreased surface tension translates to enhanced substrate wetting in actual formulations. Surface tension reduction in water-based systems is generally achieved through the addition of surfactants. Performance attributes resulting from the addition of surfactants include enhanced surface coverage, fewer defects, and more uniform distribution. Equilibrium surface tension performance is important when the system is at rest. However, the ability to reduce surface tension under dynamic conditions is of great importance in applications where high surface creation rates are utilized. Such applications include spraying, rolling and brushing of coatings or spraying of agricultural formulations, or high speed gravure or ink-jet printing. Dynamic surface tension is a fundamental quantity which provides a measure of the ability of a surfactant to reduce surface tension and provide wetting under such high speed application conditions.
Traditional nonionic surfactants such as alkylphenol or alcohol ethoxylates, and ethylene oxide (EO)/propylene oxide (PO) copolymers have excellent equilibrium surface tension performance but are generally characterized as having poor dynamic surface tension reduction. In contrast, certain anionic surfactants such as sodium dialkyl sulfosuccinates can provide good dynamic results, but these are very foamy and impart water sensitivity to the finished coating.
There is a need for a family of surfactants which provide good equilibrium and dynamic surface tension properties, are low-foaming and would be widely accepted in the coating, ink, adhesive, and agricultural formulation industries.
The importance of reducing equilibrium and dynamic surface tension in applications such as coatings, inks, and agricultural formulations is well-appreciated in the art.
Low dynamic surface tension is of great importance in the application of waterborne coatings. In an article, Schwartz, J. "The Importance of Low Dynamic Surface Tension in Waterborlie Coatings", Journal of Coatings Technology, September 1992, there is a discussion of surface tension properties in waterborne coatings and a discussion of dynamic surface tension in such coatings. Equilibrium and dynamic surface tension were evaluated for several surface active agents. It is pointed out that low dynamic surface tension is an important factor in achieving superior film formation in waterborne coatings. Dynamic coating application methods require surfactants with low dynamic surface tensions in order to prevent defects such as retraction, craters, and foam.
Efficient application of agricultural products is also highly dependent on the dynamic surface tension properties of the formulation. In an article, Wirth, W.; Storp, S.; Jacobsen, W. "Mechanisms Controlling Leaf Retention of Agricultural Spray Solutions"; Pestic. Sci. 1991, 33, 411-420, the relationship between the dynamic surface tension of agricultural formulations and the ability of these formulations to be retained on a leaf was studied. These workers observed a good correlation between retention values and dynamic surface tension, with more effective retention of formulations exhibiting low dynamic surface tension.
Low dynamic surface tension is also important in high-speed printing as discussed in the article "Using Surfactants to Formulate VOC Compliant Waterbased Inks", Medina, S. W.; Sutovich, M. N. Am. Ink Maker 1994, 72 (2), 32-38. In this article, it is stated that equilibrium surface tensions (ESTs) are pertinent only to ink systems at rest. EST values, however, are not good indicators of performance in the dynamic, high speed printing environment under which the ink is used. Dynamic surface tension is a more appropriate property. This dynamic measurement is an indicator of the ability of the surfactant to migrate to a newly created ink/substrate interface to provide wetting during high speed printing.
U.S. Pat. No. 5,098,478 discloses water-based ink compositions comprising water, a pigment, a nonionic surfactant and a solubilizing agent for the nonionic surfactant. Dynamic surface tension in ink compositions for publication gravure printing must be reduced to a level of about 25 to 40 dynes/cm to assure that printability problems will not be encountered.
U.S. Pat. No. 5,562,762 discloses an aqueous jet ink of water, dissolved dyes and a tertiary amine having two polyethoxylate substituents and that low dynamic surface tension is important in ink jet printing.
Substituted cyclic ureas have been reported to have utility in many applications. Nomura et al, Ind. Eng. Chein. Res. 1987, 26, 1056-1059, state these materials are useful as intermediates for medicines and resins and directly as chemotherapeutic agents, delignification reagents, and in cosmetics.
Likewise, U.S. Pat. No. 3,876,657 discloses 1-alkyl-2-imidazolidones (ethylene ureas) as having recognized utility as bactericides, central nervous system depressants, plant growth promoters, female fly sterilants, adhesives, textile treating agents, and as monomers for deriving polymers and copolymers.
In addition, Naumov et al, Khimiya Geteotsikl. Soedin. 1973, 1, 90-93, state these materials are useful as biologically active compounds, specifically as insecticides and insect repellents. Despite this extensive listing of utility, alkylated cyclic ureas have not been reported to have utility as surface tension reducing agents in water. In fact, Kanetani et al, Chem. Abs. 98:145450, converted long chain N-alkylimidazolidones (C8, C10, C12, C14, C16) to the propane sultone derivatives in order to make useful surfactants.
DE 4,341,984 discloses that a very large number of ureas and cyclic ureas, including N-methyl-N'-octyl propyleneurea, act as crystallization inhibitors for azole derivative fungicides, such as triazolyl methyl compounds, in aqueous solution.
U.S. Pat. No. 4,677,131 discloses substituted cyclic ureas have efficacy for enhancing drug absorption through the skin for therapeutic or diagnostic purposes. The emphasis appears to be on utilizing the strong hydrogen bonding properties for these materials.